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Questions and Answers
What is the role of folate in DNA synthesis?
What is the mechanism of action of methotrexate?
What is the main toxicity of methotrexate?
What is the mechanism of action of alkylating agents?
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What is the active form of cyclophosphamide?
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What is the adverse effect of acrolein?
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What is the mechanism of action of Vinca alkaloids in the cell cycle?
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Which Vinca alkaloid is metabolized in the liver by CYP450 3A4 and has a half-life of 5 minutes, 2 hours, and 85 hours?
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What is the primary route of excretion for vincristine sulfate?
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Which of the following adverse effects is more common in vinblastine compared to vincristine?
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What is the protein-bound percentage of vinblastine in the blood?
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Which of the following cancers is NOT commonly treated with vincristine?
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Study Notes
Folate and DNA Synthesis
- Folate is essential for DNA synthesis as it provides the necessary nucleotides for cellular division and repair.
- It plays a crucial role in the synthesis of purines and pyrimidines, which are building blocks of DNA.
Methotrexate Mechanism of Action
- Methotrexate inhibits dihydrofolate reductase, blocking the conversion of dihydrofolate to tetrahydrofolate.
- This disruption reduces the availability of folate needed for DNA and RNA synthesis, halting cell proliferation.
Main Toxicity of Methotrexate
- The primary toxicity of methotrexate is myelosuppression, leading to decreased production of blood cells, which elevates the risk of infection and bleeding.
Alkylating Agents Mechanism of Action
- Alkylating agents work by adding alkyl groups to DNA, leading to cross-linking and strand breakage.
- This process disrupts DNA replication and transcription, resulting in cell death, particularly in rapidly dividing cells.
Active Form of Cyclophosphamide
- The active form of cyclophosphamide is phosphoramide mustard, which exerts its anticancer effects after metabolic activation in the liver.
Adverse Effect of Acrolein
- Acrolein is a toxic byproduct of cyclophosphamide metabolism, primarily responsible for causing hemorrhagic cystitis, which is inflammation and bleeding of the bladder.
Vinca Alkaloids Mechanism of Action
- Vinca alkaloids inhibit microtubule formation, disrupting the mitotic spindle during cell division.
- This action prevents normal mitosis, leading to cell cycle arrest and apoptosis in cancer cells.
Vinca Alkaloid Metabolism and Half-Life
- The Vinca alkaloid metabolized by CYP450 3A4 with variable half-lives includes vincristine, which has a half-life ranging from minutes (5 minutes) to hours (85 hours).
Primary Route of Excretion for Vincristine Sulfate
- Vincristine sulfate is primarily excreted through bile and feces, with minimal renal elimination occurring.
Adverse Effects of Vinblastine vs. Vincristine
- Vinblastine is more likely to cause myelosuppression compared to vincristine, which typically has less hematologic toxicity.
Protein-Bound Percentage of Vinblastine
- Approximately 80% of vinblastine in the blood is protein-bound, affecting its distribution and therapeutic activity.
Cancers Not Commonly Treated with Vincristine
- Vincristine is not commonly used to treat certain solid tumors, such as breast or lung cancer, focusing more on hematological malignancies.
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Description
Learn about the vinca alkaloids, including vincristine, vinblastine, vindesine, and vinrosidine, derived from the periwinkle plant. Understand their mechanism of action, effects on cell division, and toxicity. This quiz covers the key aspects of these medications.
